Generating patient specific pseudo-CT of the head from MR using atlas-based regression.

Radiotherapy planning and attenuation correction of PET images require simulation of radiation transport. The necessary physical properties are typically derived from computed tomography (CT) images, but in some cases, including stereotactic neurosurgery and combined PET/MR imaging, only magnetic resonance (MR) images are available. With these applications in mind, we describe how a realistic, patient-specific, pseudo-CT of the head can be derived from anatomical MR images. We refer to the method as atlas-based regression, because of its similarity to atlas-based segmentation. Given a target MR and an atlas database comprising MR and CT pairs, atlas-based regression works by registering each atlas MR to the target MR, applying the resulting displacement fields to the corresponding atlas CTs and, finally, fusing the deformed atlas CTs into a single pseudo-CT. We use a deformable registration algorithm known as the Morphon and augment it with a certainty mask that allows a tailoring of the influence certain regions are allowed to have on the registration. Moreover, we propose a novel method of fusion, wherein the collection of deformed CTs is iteratively registered to their joint mean and find that the resulting mean CT becomes more similar to the target CT. However, the voxelwise median provided even better results; at least as good as earlier work that required special MR imaging techniques. This makes atlas-based regression a good candidate for clinical use.

[Immune tolerance induction with high-dose FVIII and pulsed intravenous immunoglobulin]. / Immuntoleranzinduktion mit hoch dosiertem FVIII und intravenösen Immunglobulin-Pulsen. Ein Patient mit Hemmkörper-Hämophilie A.

UNLABELLED: The development of neutralizing allo-antibodies against factor VIII (FVIII) or FVIII inhibitors is a severe complication in the treatment of haemophilia A. About 25% of the children with severe haemophilia A develop FVIII inhibitors. Here we report on a boy with severe haemophilia A and intron 22 inversion of the FVIII gene who was diagnosed at ten months of age. After 16 exposure days to FVIII (81 days after initial exposure) he developed a FVIII inhibitor (maximum: 9.76 BU/ml). THERAPY: We started immune tolerance induction (ITI) according to the Bonn protocol with high dose plasma derived FVIII concentrate (100 IU per kg body weight) twice daily. For additional inhibitor elimination treatment the patient received intravenous immunoglobulin (ivIg) at a dose of 1-2 g/kg body weight every 4 to 6 weeks. After start of treatment a rapid decline of the inhibitor level was observed, nevertheless low FVIII inhibitor levels persisted (<5 BU/ml). Furthermore, the FVIII half-life was still accelerated. However, after every course of ivIg the inhibitor level declined and FVIII half-life was prolonged. Currently, the FVIII half-life is approaching normal values after more than seven months of ITI duration. CONCLUSION: Additional application of immunoglobulin is beneficial for immune tolerance induction.

Quality assurance in teleradiology.

Teleradiology is the electronic transmission of radiologic images from one location to another for the purpose of interpretation or consultation. The use of teleradiology expands the responsibilities of the supervising radiologists, physicists, and engineers. Teleradiology is being utilized increasingly to provide remote primary diagnoses rather than just preliminary interpretations or overreads. Consequently, it is essential that regular quality assurance and improvement mechanisms be in place. This article details the facets of quality initiatives that should be a component of every comprehensive teleradiology program.

Congenital absence of a cervical spine pedicle: clinical and radiologic findings.

Congenital absence of a cervical pedicle is an unusual disorder with potentially confusing clinical and radiologic manifestations. A review of the previously reported 42 cases as well as 13 new cases is presented. Congenital absence of a cervical pedicle was an incidental finding in 10 of the 55 total patients (age range, 3-65 years; mean 31 years). The remainder presented with an array of symptoms; the most common was cervical pain (31 patients), often after trauma (19/31). Neurologic examination was normal in the majority (65%) of patients. The most common neurologic finding, in an additional 19% of patients, was isolated diminished sensation in an upper extremity. Imaging included conventional radiographs, tomograms, myelograms, and CT. The typical radiologic triad of findings included (1) the false appearance of an enlarged neural foramen owing to the absent pedicle; (2) a dysplastic, dorsally displaced ipsilateral articular pillar and lamina; and (3) a dysplastic ipsilateral transverse process. The spectrum of this disorder also included absence of the ipsilateral pillar in four of 55 patients and absence of the entire ipsilateral neural arch in five of 55 patients. Other osseous anomalies were present in 28 (51%) of 55 cases. In 10 of 55 cases, initial misdiagnosis resulted in inappropriate therapy, with a poor clinical outcome after therapy in three cases. Conservative therapy was the only successful management in all cases in which follow-up information was available, with the exception of one patient who had partial improvement after surgery. Careful analysis of radiologic images and knowledge of the specific findings of absent cervical pedicle should decrease the potential for misdiagnosis and inappropriate, potentially harmful therapy.

Cervical spondylolysis: imaging findings in 12 patients.

Cervical spondylolysis is defined as a corticated cleft between the superior and inferior articular facets of the articular pilar, the cervical equivalent of the pars interarticularis in the lumbar spine. Associated dysplastic changes and spina bifida suggest that the lesion is congenital. It is a rare condition; only 70 cases have been previously reported in the world literature. Recognition of this disorder and differentiation from traumatic articular pilar fracture or dislocation is of paramount importance in patients who have had cervical spine trauma. The present study details radiologic features in 12 patients 20-80 years old with cervical spondylolysis. Plain film radiologic findings were correlated with hypocycloidal high-resolution tomography (nine patients), CT (six patients), and MR imaging (one patient). Seven patients had spondylolysis at C6 (three bilateral) and five had the abnormality at C4 (all unilateral). Nine of 12 patients were initially misdiagnosed. Characteristic radiologic features include (1) a well-marginated cleft between the facets, (2) a triangular configuration of the pilar fragments on either side of the spondylolytic defect, (3) posterior displacement of the dorsal triangular pillar fragment, (4) hypoplasia of the ipsilateral pedicle, (5) spina bifida at the involved level, and (6) compensatory hyper- or hypoplasia of the ipsilateral articular pillars at the level above and/or below the defect. A multistudy approach was often necessary to demonstrate these findings. Heightened awareness of the radiologic features of cervical spondylolysis should allow one to differentiate it from articular pillar fracture or dislocation.

Experience with a prolonged respiratory care unit.

A major medical social problem at present is the need for care of patients with chronic or prolonged illness. This is particularly true in the case of respiratory disease, which has undergone major strides in prolonging life through the increased use of respirators and improved methods of medical care. In response to this need, St. Paul, Minnesota's Bethesda Lutheran Medical Center opened a prolonged respiratory care unit on Aug 21, 1979. A review and general assessment of this operation is presented. At the time of this review, the unit has been open for approximately 18 months. The obvious benefits in terms of patient care cost as well as the improvement in patient quality of life inherent in this type of specialized unit, which has an adequately trained staff, are described.